1. Field of the Invention
The present invention relates to a digital radio telephone, and more particularly to a digital radio telephone which gives information to a user in the form of speech.
2. Description of the Related Art
Recently, some telephone equipment has had a convenient function of giving users information, in the form of a synthesized voice, the information relating to, for example, instructions on use, contents of registration stored in the telephone, time, and the like. This equipment includes a speech or voice synthesizer and a memory to generate the synthesized voice.
To better understand the present invention, a brief reference will be made to a prior art telephone of this kind, shown in FIG. 1. Such a radio telephone 100 has an antenna 101, a radio telephone section 102, a handset 103, an operational section 104, a switching section 105 and a speech or voice synthesizer section 106. The radio telephone section 102 has the basic function of radio telephone communication. The switching section 105 is provided for switching over between the output of the speech synthesizer section 106 and analog speech signals during conversation from the radio telephone section 102 as voice signals to be outputted to the handset 103. The speech synthesizer section 106 is constituted by a conventional integrated circuit (IC).
For example, when the user of this radio telephone presses a function key (e.g. a speed-dial button or an one-touch dial button) of the operational section 104, the speech synthesizer section 106 detects operational information which the user inputs from the operational section 104. Then the speech synthesizer section 106 controls the switching section 105 to send out analog speech signals corresponding to the functional content of the pressed function key (e.g., the memorized telephone number) from the speech synthesizer section 106 to the handset 103, in response to the operational information.
Since this radio telephone sends out analog speech signals by utilizing the speech synthesizer section 106, there is a problem in that, as the amount of operational information increases, the memory capacity of the speech synthesizer section 106 has to be expanded to synthesize the analog speech corresponding to all of the operational information. That is, since the conventional speech synthesizer IC does not have high encoding efficiency, a large capacity memory is required, making the radio telephone expensive.